The Biodiversity of East Waka - Missouri Botanical Garden
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The Biodiversity of East Waka Missouri Botanical Garden
The biodiversity of East Waka
Prepared by Gilles Dauby and Tariq Stévart
Field team:
D. N’guema
E. Mounoumoulossi
P. Bissiemou
J. Boussiengui
Missouri Botanical Garden
Gabon 2008
2
Prologue
Missouri Botanical Garden was awarded a Central African Regional Program for the
Environment (CARPE) subcontract from the Wildlife Conservation Society (WCS) to carry
out botanical expeditions to identify Biodiversity Sanctuaries for micro-zoning in the Massif
du Chaillu landscape.
During this fiscal year Missouri Botanical Garden (MBG) has conducted two field trips in the
unexplored parts of the buffer zone of the Waka National Park. The botanical survey of the
flora was carried out by assessing the plant diversity of the East of Waka NP.
During this field trip, a total of 202 specimens have been collected, and 6 transects were done
representing 1264 individuals. The results and observations are presented here.
Tariq Stévart & Gilles Dauby
June 2008
3
Introduction to East Waka
Waka National Park is one
of the thirteen National
Parks created in 2002 in
Gabon, and one of the
three that are in the Massif
du Chaillu landscape with
Lopé and Birougou
National Parks (Fig. 1).
In order to improve the
botanical knowledge of
this region, a field survey
of 10 days has been
conducted in a botanically
unknown locality on the
East of Waka National
Park, just below Mayi
River (Fig. 2).
Fig. 1. The three National
Parks in the Massif du
Chaillu.
This region has been logged in the past (logging stopped around 10 years ago); many logging
paths and forestry roads are still in pretty good condition as we were able to observe.
The region being inventoried is
in the periphery of the Massif
du Chaillu mountain area (Fig.
2). The topography is not
particularly rugged, with
altitudes ranging from 550 to
700 m. The locality presents a
strong difference of
topography. Gentle valleys
with small streams and large
swamps especially abundant in
Maranthaceae and Begoniaceae
alternate with hill tops and
hillsides covered in terra firme
rain forests. Annual rainfall is
2100 mm on average (Fig. 3).
Fig. 2. Locality of East of Waka
and position of the 6 transects.
4
Fig. 3. Annual rainfall in Gabon (Hijmans et al., 2005)
Monts de
Cristal
Chaillu
Massif
Fig. 4. Altitude distribution and localization of the Waka NP and the two massifs in Gabon: Monts de
Cristal and Massif du Chaillu.
5
Methods
Transects used to record species composition were 200 m long and 5 m wide. Every individual with a
diameter at breast height (dbh) of 5 cm or more was recorded and identified. In addition to individuals
present in the transect, we added 100 individuals that belong to the upper canopy stratum present on both
sides of the transect. For each individual not identified in the field, a specimen was collected for
identification in the herbariums of Libreville and Brussels. In several cases, we could not assign a specific
name for individuals; we therefore classified those individuals as morpho-species. For each individual, the
stratum to which it belongs (either dominant tree or lower canopy trees) was noted.
The transects were carried out in terra firme mature forests, separated from each other by at least 1 km, and
distributed in the various topographical positions.
We also collected every plant in fruit or flowering with as many duplicates as possible. Duplicates will be
distributed to the following herbariums (LBV, MO, WAG and BR).
Local diversity or diversity alpha has been estimated by rarefaction principles (Gotelli and Colwell, 2001).
Based on rarefaction curves (successive re-samplings of the pool of N individuals at random and plotting of
the average number of species and number of individuals), we can obtain an unbiased diversity index for a
fixed number of re-sampled individuals (=k). For example, for a k=50 we obtain the expected number of
species for 50 individuals randomly chosen in the pool. This index was computed with the BiodivR software
written by Hardy (2005). We also computed local diversity by using the fisher alpha index.
Similarities between transects were computed using the Morisita-Horn similarity index with BiodivR
software (Hardy, 2005) and a dendrogram was calculated.
For a similarity measure between samples i and j, Pis is the frequency of the
species S in sample i.
6
Results
Results
General characteristics
1264 individuals were inventoried in all transects, representing 39 different families (one
individual is unidentified at the family level), 165 species and morpho-species (91 individuals
are not yet identified, and several species are very likely to be added later).
Dominant families in number of species were Caesalpiniaceae and Euphorbiaceae (Fig. 5).
Euphorbiaceae, Burseraceae and Caesalpiniaceae represent more than half of the total of
inventoried individuals. However, if we consider lower and upper canopy trees separately,
there is a shift in tree composition. The lower stratum is dominated by Euphorbiaceae and
Clusiaceae, both mainly represented by the species Conceveiba macrostachys and Garcinia
spp. respectively (Fig. 6). Both families are no longer dominant when considering upper
canopy trees only. For upper canopy trees, 4 families represent 75 % of all individuals:
Burseraceae (mainly Aucouma klaineana and Dacryodes spp.), Caesalpiniaceae,
Myristicaceae (Staudtia kamerunensis and Coelocaryon preussii) and Olacaceae (Fig. 7).
Similarity
Transect 10 shows a much higher diversity than other transects. The dendrogram based on a
similarity matrix shows that this transect has a floristic composition which differs from other
transects (Fig. 4.). All other transects are relatively similar in terms of floristic composition.
Number of Specific Altitude Topography Fischer
Transect individuals richness (m) position alpha S (k=50)
GD5 209 56 535 hillside 25,73 25,12
GD6 207 62 565 hillside 31,36 26,97
GD7 230 62 540 hillside 29,21 23,78
GD8 214 55 575 hill top 24,67 25,45
GD9 196 53 570 hillside 24,37 25,05
GD10 198 74 530 valley 43,78 33,51
7
Dominant families in transect for number of species
Caesalpiniaceae;
20; 12%
Others; 65; 40% Euphorbiaceae;
19; 12%
Clusiaceae; 12;
7%
Annonaceae; 10;
Scytopetalaceae; 6%
5; 3%
Mimosaceae; 6;
Burseraceae; 10;
4% Rubiaceae; 9; 5% Fig. 5. Dominant families in
Olacaceae; 9; 5% 6%
terms of numbers of species
in transects.
Dominant families in transect for numbers of individuals :
lower canopy trees
Others; 72; 14%
Moraceae; 9; 2%
Rubiaceae; 14; Euphorbiaceae;
3% 200; 38%
Annonaceae; 28;
5%
Olacaceae; 39;
8% Clusiaceae; 71;
14%
Fig. 6. Dominant families in
Burseraceae; 42; Caesalpiniaceae;
terms of numbers of individuals
8% 44; 8%
for lower canopy trees.
Dominant families in transect for numbers of individuals :
upper canopy trees
Scytopetalaceae; Others; 74; 10%
Burseraceae;
13; 2%
Mainly Okoum é
Annonaceae; 19; 186; 24%
3%
Mimosaceae; 35;
5%
Euphorbiaceae;
Caesalpiniaceae;
56; 8%
151; 20%
Olacaceae; 104; Fig. 7. Dominant families in
Myristicaceae;
14% terms of number of individuals
106; 14%
for upper canopy trees.
8
60
Monts de Cristal Waka Littoral
50
40
Fisher alph
30
20
10
0
Mt mbilan Ngol Mt mbilan Bouvala Balendi East of Mondah Pongara
(n=7) maduaka plateau (n=6) (n=6) Waka (n=5) (n=7)
(n=4) (n=4) (n=6)
Fig. 8. Mean local diversity (expressed as fisher alpha index) for 8 Gabonese localities located in 3 regions of
Gabon
Tr 10 valley
Tr 9 Hill side
0,75
0,75
0,50
0,50 Tr 8 Hill top
0,85
0,85
0,65
0,65 Tr 7 Hill side
0,65
0,65
Tr 6 Hill side
Tr 5 Hill side
0,400
0,500
0,300
0,200
0,600
0,100
0
Similarity (Morisita-Horn index)
Fig. 9. Clustering dendrogram of the 6 transects obtained from a similarity matrix computed by the Morisita
Horn similarity index.
9
Discussion
Similarity
Based on the Morisita-Horn similarity index, transect 10 differs clearly from all other
transects. The topographical position seems to be a strong ecological gradient to explain this
difference. However, we also noted the presence of many gaps (old trees which had fallen
down) around the transect, even though we tried to avoid it. Gaps dynamic may influence
local diversity by allowing shade-tolerant and light-demanding tree species to coexist (Leigh
et al., 2004). The other transects do not differ significantly from each other.
Local diversity
Mean local diversity expressed with fisher alpha was compared to other localities in three
different regions: the littoral around Libreville, Monts de Cristal and Waka/Chaillu Massif.
The East of Waka locality is the less diverse locality in Waka region. These results suggest
ecological gradients play a major role in explaining this pattern of diversity. Indeed, the
localities of Bouvala and Balendi are both in two landscapes with a very complex topography
and relatively high mountains (see previous reports), contrary to the locality of East of Waka.
This hypothesis is somehow confirmed when local diversity in Waka is compared to Monts de
Cristal, which also possesses a complex topography.
Conclusion
Despite the fact that the locality explored has been logged in the recent past (roughly 10
years ago), there are still large areas of mature and undisturbed rainforests. Local diversity
is not particularly high compared to mountainous localities in Waka region, but this
locality’s topography differs from that of the inner part of the Waka NP. Theses forests
are probably one of the last remnants of rich in Okoumé lowland rainforest present in the
area. However, more investigation is needed in this part of the buffer zone of the Waka
NP in order to localize the remnant block of lowland forest that could be established as
Biodiversity Sanctuaries more precisely.
Moreover, these additional data will also allow us to calculate the beta diversity which
estimates the relative effects of geographical and ecological distance to explain species
turn-over.
10General collecting
Full identification of the 202 specimens (representing at least 156 species) collected during
this mission is still ongoing and revealing some interesting findings since we already found
out two new records for Gabon.
The fern Elaphoglossum kuhnii Hieron (Lomariospidaceae) is newly recorded in Gabon (Fig.
5.). This species is a typical species of submountain forests, and was formerly found only on
Mt Cameroun and Mt Nimba in Liberia at altitudes higher than 800 m. In Gabon, it was found
at only 450 m in a very humid swampy forest in a valley. This habitat is probably a sub-
optimal habitat for this species. Typical submoutain species are often transgressive species in
swampy forests at lower altitudes (Senterre, 2005).
Fig. 10. Elaphoglossum kuhnii Hieron
(Lomariospidaceae), new national
record for Gabon
The other new record in Gabon is Tricalysia trachycarpa Robbr. (Rubiaceae) (Fig. 6.). This is
the second known locality for this species. It was previously found in the Central province of
Congo Kinshasa (Robbrecht, 1983) and thus possesses a strong disjunctive distribution.
Fig. 6. Tricalysia trachycarpa Robbr.
(Rubiaceae), a new national record for
Gabon.
11We also collected and identified several species endemic to Gabon.
Amphiblemma hallei Jacq.-Fél. (Melastomataceae) is a shrub present in the rainforest
understoreys, especially in very humid valleys. According to Sosef et al 2006 East Waka is
the seventh known locality for this species (Fig. 7). Its distribution is restricted along a South-
North axis, from Monts de Cristal to Chaillu massif, matching the Oriental Atlantic
phytogeographical district recognized by several authors (see Senterre 2005).
Fig. 7. Amphiblemma hallei Jacq.-Fél. (Melastomataceae, left) and distribution of this species, endemic
Fig. 8. Anonidium floribundum
Pellegr. (Annonaceae) A species
subendemic to Gabon
Fig. 9. Bertiera arctistipula N.Hallé
(Rubiaceae) species endemic to Gabon
12Acknowledgements
This report is made possible by the generous support of the American people through the United States
Agency for International Development (USAID) and the Wildlife Conservation Society under the
USAID co-operative agreement reference 623-A-00-06-00067-00. The contents are the responsibility
of the Missouri Botanical Garden and do not necessarily reflect the views of USAID, the United States
Government or the Wildlife Conservation Society.”
Fieldwork activities are made with the support of the Herbier National du Gabon (IPHAMETRA)
under the permission of the CENAREST. The checklist of Waka NP project was funded by the
Beneficia Foundation. Orchid researches in the Massif du Chaillu are funded by the American Orchid
Society and the Conservation Committee of the San Diego County Orchid Society. We are grateful to
Elmar Robbrecht (National Botanical Garden of Belgium) for identifying our Tricalysia (Rubiaceae),
Charlemagne N’Guembou for identifying Bertiera species and Olivier Lachenaud for identifying other
Rubiaceae.
References
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species richness. Ecology Letters 4: 379-391
Hardy OJ (2005) BiodivR 1.0. A program to compute statistically unbiased indices of species diversity within sample and
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